Question

我最近开始学习OpenGL，我一直在尝试编写一个程序，使用VAO和带有着色器的VBO在屏幕上显示菱形。我的代码主要基于本教程： https://www.opengl.org/wiki/Tutorial2:_VAOs,_VBOs,_Vertex_and_Fragment_Shaders_%28C_/_SDL%29 我还使用了教程中的着色器。假设钻石是使用顶点数组对象的颜色信息绘制的，而是仅使用白色绘制。着色器似乎加载正常，所以我认为这是我的顶点和缓冲区数组对象的问题。有人可以解释为什么我的代码没有按预期工作或显示如何使用颜色属性数组中的颜色渲染VAO的明确示例。

package windows;

import java.awt.Frame;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;

import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.GLProfile;
import javax.media.opengl.awt.GLCanvas;
import javax.media.opengl.glu.GLU;

import shaders.ShaderControl2;

import com.jogamp.common.nio.Buffers;

public class Test4 implements GLEventListener{

ShaderControl2 sc;
FloatBuffer vertexPos, vertexCol;
IntBuffer vao, vbo; 
GLU glu = new GLU();

public static void main(String[] args){
    GLProfile glp = GLProfile.getDefault();
    GLCapabilities caps = new GLCapabilities(glp);
    GLCanvas canvas = new GLCanvas(caps);

    Test4 t = new Test4();

    canvas.addGLEventListener(t);

    Frame f = new Frame("TEST #4");
    f.setSize(400,400);
    f.add(canvas);
    f.setVisible(true);
    f.addWindowListener(new WindowAdapter(){
        public void windowClosing(WindowEvent e){
            System.exit(0);
        }
    });
}


@Override
public void display(GLAutoDrawable drawable) {
    GL2 gl = drawable.getGL().getGL2();
    gl.glClearColor(0, 0, 0, 1f);
    gl.glClear(GL2.GL_COLOR_BUFFER_BIT);

    sc.useShader(gl);

    gl.glBindVertexArray(vao.get(0));
    gl.glEnableVertexAttribArray(0);
    gl.glEnableVertexAttribArray(1);
    gl.glDrawArrays(GL2.GL_LINE_LOOP, 0 , 4);

    sc.dontUseShader(gl);

}

@Override
public void dispose(GLAutoDrawable drawable) {
    // TODO Auto-generated method stub

}

@Override
public void init(GLAutoDrawable drawable) {
    GL2 gl = drawable.getGL().getGL2();
    System.out.println(gl.glGetString(GL2.GL_VERSION));

    vertexPos = Buffers.newDirectFloatBuffer(8);
    vertexPos.put(new float[]{0f, 1f});
    vertexPos.put(new float[]{1f, 0f});
    vertexPos.put(new float[]{0f, -1f});
    vertexPos.put(new float[]{-1f, 0});
    vertexPos.flip();

    vertexCol = Buffers.newDirectFloatBuffer(12);
    vertexCol.put(new float[]{1f, 0f, 0f});
    vertexCol.put(new float[]{0f, 1f, 0f});
    vertexCol.put(new float[]{0f, 0f, 1f});
    vertexCol.put(new float[]{1f, 1f, 1f});
    vertexCol.flip();

    vao = IntBuffer.allocate(1);
    vbo = IntBuffer.allocate(2);

    gl.glGenVertexArrays(1, vao);
    gl.glGenBuffers(2, vbo);

    int bytesPerFloat = Float.SIZE/Byte.SIZE;

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER,  vbo.get(0));
    gl.glBufferData(GL2.GL_ARRAY_BUFFER, vertexPos.capacity() * bytesPerFloat, vertexPos, GL2.GL_STATIC_DRAW);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, vbo.get(1));
    gl.glBufferData(GL2.GL_ARRAY_BUFFER, vertexCol.capacity() * bytesPerFloat, vertexCol, GL2.GL_STATIC_DRAW);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, 0);

    gl.glBindVertexArray(vao.get());
    gl.glEnableVertexAttribArray(0);
    gl.glEnableVertexAttribArray(1);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, vbo.get(0));
    gl.glVertexAttribPointer(0, 2, GL2.GL_FLOAT, false, 0, 0);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, vbo.get(1));
    gl.glVertexAttribPointer(1, 3, GL2.GL_FLOAT, false, 0, 0);

    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, 0);


    sc = new ShaderControl2();
    sc.vSrc = sc.loadShader("v.txt");
    sc.fSrc = sc.loadShader("f.txt");

}

@Override
public void reshape(GLAutoDrawable drawable, int x, int y, int width,
        int height) {

}

}

ShaderControl2代码：

package shaders;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.IntBuffer;

import javax.media.opengl.*;

public class ShaderControl2 {

private int vertexShaderProg, fragmentShaderProg, shaderProg;
public String[] vSrc, fSrc;

public String[] loadShader(String sFile){
    String line = new String();
    StringBuilder fileContent = new StringBuilder();

    try{
        InputStream is = getClass().getResourceAsStream(sFile);
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        while((line = br.readLine()) != null){
            fileContent.append(line + "\n");
        }
        is.close();
    } catch(Exception e){
        e.printStackTrace();
    }
    System.out.println("Shader file content:\n" + fileContent);
    return new String[]{fileContent.toString()};
}

public void attachShader(GL2 gl){
    IntBuffer isCompiledVS = IntBuffer.allocate(1), isCompiledFS = IntBuffer.allocate(1), isLinked = IntBuffer.allocate(1);
    IntBuffer vLogLength = IntBuffer.allocate(1), fLogLength = IntBuffer.allocate(1), linkLogLength = IntBuffer.allocate(1);
    ByteBuffer vertexInfoLog, fragmentInfoLog, linkInfoLog;
    int size;

    vertexShaderProg = gl.glCreateShader(GL2.GL_VERTEX_SHADER);

    gl.glShaderSource(vertexShaderProg, 1, vSrc, null);
    gl.glCompileShader(vertexShaderProg);

    gl.glGetShaderiv(vertexShaderProg, GL2.GL_COMPILE_STATUS, isCompiledVS);
    if(isCompiledVS.get(0) == 0){
        System.out.println("Failed to compile vertexShaderProg");

        gl.glGetShaderiv(vertexShaderProg, GL2.GL_INFO_LOG_LENGTH, vLogLength); 
        size = vLogLength.get(0);
        vertexInfoLog = ByteBuffer.allocate(size);
        gl.glGetShaderInfoLog(vertexShaderProg, size, vLogLength, vertexInfoLog);

        for(byte b : vertexInfoLog.array()){
            System.err.print((char)b);
        }
    }

    fragmentShaderProg = gl.glCreateShader(GL2.GL_VERTEX_SHADER);

    gl.glShaderSource(fragmentShaderProg, 1, vSrc, null);
    gl.glCompileShader(fragmentShaderProg);

    gl.glGetShaderiv(fragmentShaderProg, GL2.GL_COMPILE_STATUS, isCompiledFS);
    if(isCompiledFS.get(0) == 0){
        System.out.println("Failed to compile fragmentShaderProg");

        gl.glGetShaderiv(fragmentShaderProg, GL2.GL_INFO_LOG_LENGTH, fLogLength);   
        size = fLogLength.get(0);
        fragmentInfoLog = ByteBuffer.allocate(size);
        gl.glGetShaderInfoLog(fragmentShaderProg, size, fLogLength, fragmentInfoLog);

        for(byte b : fragmentInfoLog.array()){
            System.err.print((char)b);
        }

    }

    shaderProg = gl.glCreateProgram();
    gl.glAttachShader(shaderProg, vertexShaderProg);
    gl.glAttachShader(shaderProg, fragmentShaderProg);

    gl.glBindAttribLocation(shaderProg, 0, "in_Position");
    gl.glBindAttribLocation(shaderProg, 1, "in_Color");

    gl.glLinkProgram(shaderProg);

    gl.glGetProgramiv(shaderProg, GL2.GL_LINK_STATUS, isLinked);
    if(isLinked.get(0) == 0){
        System.out.println("Failed to link shaderProg");

        gl.glGetShaderiv(shaderProg, GL2.GL_INFO_LOG_LENGTH, linkLogLength);
        size = linkLogLength.get(0);
        linkInfoLog = ByteBuffer.allocate(size);
        gl.glGetProgramInfoLog(shaderProg, size, linkLogLength, linkInfoLog);

        for(byte b : linkInfoLog.array()){
            System.err.print((char)b);
        }
    }       
}

public int useShader(GL2 gl){
    gl.glUseProgram(shaderProg);
    return shaderProg;
}

public void dontUseShader(GL2 gl){
    gl.glUseProgram(0);
}
}

着色器代码

f.txt：

#version 210
// It was expressed that some drivers required this next line to function properly
precision highp float;

in  vec3 ex_Color;
out vec4 gl_FragColor;

void main(void) {
    // Pass through our original color with full opacity.
    gl_FragColor = vec4(ex_Color,1.0);
}

v.txt：

#version 210
// in_Position was bound to attribute index 0 and in_Color was bound to attribute index 1
in  vec2 in_Position;
in  vec3 in_Color;

// We output the ex_Color variable to the next shader in the chain
out vec3 ex_Color;
void main(void) {
// Since we are using flat lines, our input only had two points: x and y.
// Set the Z coordinate to 0 and W coordinate to 1

gl_Position = vec4(in_Position.x, in_Position.y, 0.0, 1.0);

// GLSL allows shorthand use of vectors too, the following is also valid:
// gl_Position = vec4(in_Position, 0.0, 1.0);
// We're simply passing the color through unmodified

ex_Color = in_Color;
}

Answer 1

您只看到白线的原因是因为没有使用着色器程序。

我无法看到你在哪里调用附着着色器（你从不调用sc.attachShader（gl），我在init方法的末尾添加了sc.attachShader（gl）。

现在会出现很多错误。

在attachshader中，当您创建fragmentShaderProg时，您将其创建为GL_VERTEX_SHADER，它应该是GL_FRAGMENT_SHADER，就在您发送顶点着色器的源代替片段着色器的下方。

GLSL语言版本210不存在，将其更改为版本130. GLSL版本的内容是它独立于OpenGL版本，https://github.com/mattdesl/lwjgl-basics/wiki/GLSL-Versions

#version 130

现在添加到init方法的末尾

sc.attachShader(gl)

并更改

fragmentShaderProg = gl.glCreateShader(GL2.GL_VERTEX_SHADER);
gl.glShaderSource(fragmentShaderProg, 1, vSrc, null);

的

fragmentShaderProg = gl.glCreateShader(GL2.GL_FRAGMENT_SHADER);
gl.glShaderSource(fragmentShaderProg, 1, fSrc, null);

现在可行。

working result

VAO不会使用着色器呈现颜色

1 个答案: